Browsing by Author "Hsiao, YS"

Now showing 1 - 3 of 3

A single mutation converts the nucleotide specificity of phenol sulfotransferase from PAP to AMP
(2002-10-29)
Hsiao, YS
;
Yang, YS
;
生物科技學系
;
Department of Biological Science and Technology
Sulfotransferases (STs) catalyze all the known biological sulfonations, in which a sulfuryl group from a common sulfonate donor such as 3'-phosphoadenosine 5-phosphosulfate (PAPS) is transferred to a nucleophilic acceptor. In addition to PAPS, phenol sulfotransferase (PST), a member of the ST family, utilizes other nucleotides as substrates with much less catalytic efficiency [Lin, E. S., and Yang, Y. S. (2000) Biochem. Biophys. Res. Commun. 271, 818-822]. Six amino acid residues of PST have been chosen for mutagenesis studies on the basis of a model of PST and its sequence alignment with those of available cytosolic and membrane-anchored STs. Systematic analyses of the mutants reveal that Ser134 is important for the regulation of nucleotide specificity between 3'-phosphoadenosine 5'-phosphate (PAP) and adenosine 5'-monophosphate (AMP). Kinetic studies also indicate that Ser134 plays a key role in nucleotide binding (K-m) but not in catalysis (k(cat)). Consequently, the catalytic efficiency (k(cat)/K-m) of PST can be altered by 5 orders of magnitude with a mutation of Ser134. Moreover, the change in nucleotide specificity from PAP to AMP can be achieved by mutation of Ser134 to any of the following residues: Glu, Gln, Arg, and His. Roles of Lys44, Arg126, and Arg253, which interact directly with the 5'- and 3'-phosphate of PAP, were also investigated by mutagenesis and kinetic experiments. On the basis of these findings, we suggest that Ser134 is the key residue that enables PST to discriminate PAP from AMP.
Orthometric corrections from leveling, gravity, density and elevation data: a case study in Taiwan
(2003-08-01)
Hwang, C
;
Hsiao, YS
;
土木工程學系
;
Department of Civil Engineering
A new orthometric correction (OC) formula is presented and tested with various mean gravity reduction methods using leveling, gravity, elevation, and density data. For mean gravity computations, the Helmert method, a modified Helmert method with variable density and gravity anomaly gradient, and a modified Mader method were used. An improved method of terrain correction computation based on Gaussian quadrature is used in the modified Mader method. These methods produce different results and yield OCs that are greater than 10 cm between adjacent benchmarks (separated by similar to2 km) at elevations over 3000 in. Applying OC reduces misclosures at closed leveling circuits and improves the results of leveling network adjustments. Variable density yields variation of OC at millimeter level everywhere, while gravity anomaly gradient introduces variation of OC of greater than 10 cm at higher elevations, suggesting that these quantities must be considered in OC. The modified Mader method is recommended for computing OC.
Terrain correction computation using Gaussian quadrature
(2003-12-01)
Hwang, CW
;
Wang, CG
;
Hsiao, YS
;
土木工程學系
;
Department of Civil Engineering
A method and a program (tcq) in FORTRAN 90 based on Gaussian quadrature are developed to compute the terrain correction (TC). TCs were determined on 1010 benchmarks using the Gaussian quadrature, prism and FFT methods using a 3" x 3" elevation grid for the inner zone and a 30" x 30" elevation grid for the outer zone. In order to achieve a 0.1 mgal accuracy in TC while reducing the computing time, the best inner and outer radii for TC computation are 20 and 200 km, respectively. The Gaussian quadrature is a highly accurate numerical integrator and yields results that outperform those from the prism method and the FFT method. The singular problem of the kernel function in TC is treated by considering the innermost zone effect, which can be expressed as a complete elliptic integral of the first kind. The innermost zone effect must be taken into account if the required accuracy of TC is at a 1-mgal level. (C) 2003 Elsevier Ltd. All rights reserved.